Electrohydraulic servo unit



3 Sheets-Sheet 1 W. D. TEAGUE, JR

ELECTROHYDRAULIC SERVO UNIT mm a 1 Feb. 17, 1953 Filed Feb. 14, 1947 INVENTOR. W; 1 72-7? 0. 7m 6(/[, JR. W 1/ m A 770/? E Y Feb. 17, 1953 Filed Feb. 14, 1947 W. D. TEAGUE, JR'

3 Sheets-Sheet 3 FIG. 7

TRANSMITTER HYBRAJLI'c AMPLIIFIER o g MOTOR FOLLOWUP W l I06 24 2.0

TRANSMITTER I0 1; o o- HYDRAULIC AMPLIFIER 3@ FOLLOW UP MOTOR I06 I l H2 54 E FIG. 9 5 56a.

XZUZ/ 6 IN V EN TOR.

HTTOk/VE) Patented Feb. 17, 1953 UNITED STATES PATENT OFFICE ELECTROHYDRAULIC SERVO UNIT Walter Dorwin Teague, J r., Alpine, N. J assignor to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application February 14, 1947, Serial No. 728,589

3 Claims. (Cl. 121-41) The invention hereof relates to electrohydraulic servo units, and particularly to a unit of this character by which a lever or other operating member may be actuated in response to a signal from a remotely located control device, such as an airplane control part.

Among the objects of the invention are to overcome disadvantages of prior servo units and to do so by novel efiective means.

Another object is to provide a servo unit by which the lever or operating member may be positioned accurately and rapidly against a resisting torque in response to the signal.

Other objects are to eliminate usual connecting lines, provide novel means for translating between rotary and linear motion, and to combine a drive motor, a pilot valve, a main iston and a follow up device in a compact unit.

Another object is to provide a system which is more stable than a conventional system, as by making the main piston position proportional to the pilot valve position.

Another object is to provide a unit which is more flexible in the selection and location of its parts.

Another object is to provide a device of the above indicated character which is simple and durable in construction, economical to manufacture, and effective in its operation.

These and other objects and features of the invention are pointed out in the following description in terms of the embodiment thereof which is shown in the accompanying drawings. It is to be understood, however, that the drawings are for the purpose of illustration only, and are not designed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings:

Figure l is a side view partially in elevation and partially in section of an electro hydraulic servo unit constructed in accordance withthe l invention in one form;

Figure 2 is an enlarged fragmentary view of a portion of the structure as seen in Figure 1;

Figure 3 is a section taken substantially along the line 33 of Figure 2;

Figure 4 is a view similar to Figure 2 of a modification of the structure thereof;

Figure 5 is aview similar to Figure 1, taken 2 substantially along the line 5-5 of Figure 6, of the invention in further modified form;

Figure 6 is an enlarged section taken substantially along the line 6-6 of Figure 5;

Fig. '7 is a diagrammatic illustration of the embodiment of the invention shown in Fig. 1;

Fig. 8 is a diagrammatic illustration of the embodiment of the invention shown in Fig. 5; and

Fig. 9 is a section taken along line 9--9 of Fig. 1.

Referring to Figure 1, the device of the form shown comprises in general, a variable phase driving motor l0 operative in response to a signal from a transmitter Illa, a pilot valve drive screw i2, a tubular pilot valve element i4, a main piston iii, a follow-up device drive I8, a follow-up device 20, and a torque output lever 22.

The remote control transmitter Illa forms no part of the present invention and any transmitter capable of inducing an electrical signal upon a displacement thereof from a null position may be used. Similarly, the variable phase drivin motor l0 and follow-up device 20 per so are not shown or described since these elements are well known in the art. The only requirement of these elements necessary to the carrying out of the instant invention is that the motor In is capable of operation in response to a signal from the transmitter Illa, and the follow-up device 20 is capable of cancelling out the signal of the transmitter upon reaching a position in agreellraent with a displaced position of the transmitter Specifically, the form of Figure 1 comprises a housing body 24 having, successively therealong from one end, from left to right as shown, in the order named, opposite side apertures 26, a partition 28, and a cylinder 30 having a fluid pres-sure side inlet port 32, and a closure 34 for the left hand end of the drive as shown.

A housing member 36 comprises a closedend 38 telescoping the other, or right-hand, enact the body 24, a mounting portion 40 at the other end of the housing member 35, and an intermediate wall 42 cooperating with the closed end 38 izc form a chamber 44 having a side drain port The follow-up device 20 in the portion 40, includes a rotor shaft 48 operable through a seal 50 in the wall 42. The motor I is mounted on, and has a shaft 52 operable through the closure 34. The lever 22 includes arms 54 extending laterally of one side, the top as shown, of the housing body 24, and a split-yoke 56 embracing the body having legs 58 opposite the apertures 25 pivoted to the body, as by a shaft or pin 60, at a side of the body, the underside, as shown, opposite the arm 54 intermediate the apertures 26. The split-yoke 55 being joined together adjacent its ends by bolts 56a, shown in Figure 9.

The tubular pilot valve element I4 ha an internal screw thread portion 62 next to the motor I0 cooperating with a nut 64 having a shank 63 by which it is connected to the motor shaft 52.

The piston It, in the cylinder 30, is provided with a compartment 58, between the ends of the piston, open to the pressure port 32, and has a central bore 10 by which the piston axially slidably surrounds the valve element I4. The piston I includes a hollow extension 12 and a. tubular stem element 14 continuing the bore oppositely from the piston through the partition 23 and the closed end 38, respectively. A member I6, fixed to the extension i2 by a pin Ha, shown in Figure 9, extends, laterally oppositely of the extension 12, through the apertures 26 and is pivotally mounted in bearings a carried by the legs 58 of the lever 22.

A plurality of pairs of passage 18 and each form one passage between the valve element It and the cylinder 30 at one side of the piston I 5, and a plurality of pairs of similar passages 82 and 84 each form a passage between the valve element I4 and the cylinder 30 at the opposite side of the piston.

The extension I2 and the stem 14 have cylinder outlets 86 and 88, respectively. The valve element I4 has side cut outs 90 and 92 which, with adjacent lands on the valve are adapted to alternately open and close the piston passages 80 and 84, and ducts 94 and 96 are similarly adapted to alternately close and open the cylinder outlets 86 and 08, respectively, to drain through and along the valve element I4 to the chamber 44 and the drain port 46. Ducts 95 are provided to prevent leakage to the left, as shown, between the extension I2 and the valve element I4, and to direct fluid from the ducts 95 through the valve element to the chamber 44.

A ball bearing long-lead crew-and-nut connection 98, as better seen in Figures 2 and 3, in this instance, is connected between the stem element 14 and the shaft 48 of the follow-up device 20.

In operation, if the remote control transmitter Illa is turned to a new position, the signal thus induced is fed to an amplifier IDb, shown diagrammatically in Figure 7 and the motor I0 is caused to rotate in the correct direction to correspondingly drive the pilot valve I4 through the screw and nut 62 and 64, respectively,

Shifting of the pilot valve I4, from the null position shown, causes oil to fiow to the desired end of the piston I8 to effect pressure at such end, and'connects the opposite end of the piston to drain. V

The piston I5 moves the lever 22, and acts through the long-lead screw connection '98 to turn the shaft 48 until the follow-up device 20 is again in agreement with the transmitter Illa, which action cuts out the signal to the amplifler I027. The motor I0 stops, the valve I4 stops, and the piston I6 stops in a new position so that 4 its ports are covered by the lands on the pilot valve I4.

As indicated in Figure 4, the shaft 48, instead of being driven by the piston stem 14, as above set forth, is driven directly by the valve element I4.

In Figures 5 and 6, the servo unit is shown in a modified form, and the hydraulic motor is of a rotary type instead of the linear type above set forth. Moreover, in this embodiment the relative positions of the electric motor I0, follow-up device 20 and hydraulic motor have been changed. As shown in Fig. 5, the follow-u device 20 is carried within a housing I 35 that is secured to a side of the hydraulic motor casing II2. A gear box I35 is secured to the opposite side of the housing I35 and the motor I0 is secured to this gearbox I38. Thus, in this embodiment, the relative positions of the elements of the servo unit are as follows: on the left extremity, motor I0, in the center, follow-up device 20; and at the right extremity, the hydraulic motor. The motor In is connected through suitable gearing I00 located in the gear box I38, to the shaft of the follow-up device 20. As shown diagrammatically in Figure 8, the motor I0 is electrically connected to a transmitter I021 and controlled by an electrical signal from said transmitter Illa. The follow-up device 20 is also electrically connected to said transmitter Illa and adapted to cancel or wipe out the signal of the transmitter [0a.

A rotary valve stem I06, connected to a shaft 2'58 of the follow-up device, is rotatable within a valve sleeve IIII. The hydraulic motor casing I I 2 is provided with a pressure conduit I I4 and a drain conduit II6 connected to a source of liquid under pressure and a sump, respectively. Radial valve pistons II? are connected to the sleeve I IO to move therewith between radial dams I20, acting as cylinder heads to develop torque.

The valve I06 contains two pairs of pressure slots I22 and one pair of drainer exhaust slots I24. The sleeve III] is provided with four longitudinally spaced radial holes I 26, the inner ends of which cooperate with the valve slots I22 and I24 to connect the opposite sides of radial pistons I I8 to pressure and drain as required to have the sleeve IIO follow the movements of the rotary stem I06.

The sleeve H0 is connected to a sun gear I20 which engages planetary gears I30 rotatably mounted on a final control lever I02, gears I30 also engaging a ring gear I32 to provide a stage of planetary gear reduction, with the result that the lever I02 moves with increased torque through a smaller angle than the vanes IIB.

The end of thesleeve I I0 is connected to drain through holes I34 lengthwise in the valve-stem I06, and connected to the drain slots I24.

The device of Figures 5 and 6 differs from the devices of the previous figures as'shown, in that the follow-up device 20 is directly driven by the motor I0, instead of by the piston I6, with a consequent increase of stability in the subcombination comprising the motor I0, the follow-up device 20 and the rotary valve I06, which otherwise tends to go into high-frequency oscillation, as on the order of twenty cycles per second, upon receiving a jolt or sharp impulse.

Such stability is also obtained with the form of Figure 4. H

However, within the invention, any of the fol- 7, hula-11 valve element, tq operete the-,pieton and thus move the 1eve1' -to; a gosition in agreement with the displacement of said transmitter.

WALTER. DQRWINTEAGUE, JR.

5 REFERENCES CITED The following, references; are of; recprd-in the file of; this patent-:

UNITED STATES PATENTS m Number Name Date 1,377,306 Brush May 10, 1921 1,790,620 Davis Jan. 27, 1931 1,959,177 Sassen, May 15', 1934 2,131,481 OCpnnor Sept, 27; 1938 15 Number 8 Name Date Hodgman Oct. 10, 1939 Riggs. Oct. 17, 1939 Fischer Nov. 11, 1941 Muller Apr. 27, 1943 Weathers Mar. 14, 1944 Pohl Sept. 18, 1945 Hultin May 22, 1945 Gille July 16, 1946 Brown Oct. 15, 1946 Spencer Dec. 10, 1946 Hansen Feb. 18, 1947 Hart; July 15, 1947 Ingoldby May 4, 1948 

